/**
 * IK 中文分词  版本 5.0.1
 * IK Analyzer release 5.0.1
 * 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * 源代码由林良益(linliangyi2005@gmail.com)提供
 * 版权声明 2012，乌龙茶工作室
 * provided by Linliangyi and copyright 2012 by Oolong studio
 * 

 * 
 */
package org.wltea.analyzer.lucene;

import java.io.IOException;
import java.io.Reader;

import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;

import org.wltea.analyzer.core.IKSegmenter;
import org.wltea.analyzer.core.Lexeme;

/**
 * IK分词器 Lucene Tokenizer适配器类
 * 兼容Lucene 4.0版本
 */
public final class IKTokenizer extends Tokenizer {

  // IK分词器实现
  private IKSegmenter _IKImplement;

  // 词元文本属性
  private final CharTermAttribute termAtt;
  // 词元位移属性
  private final OffsetAttribute offsetAtt;
  // 词元分类属性（该属性分类参考org.wltea.analyzer.core.Lexeme中的分类常量）
  private final TypeAttribute typeAtt;
  // 记录最后一个词元的结束位置
  private int endPosition;

  /**
   * Lucene 4.0 Tokenizer适配器类构造函数
   * @param in
   * @param useSmart
   */
  public IKTokenizer(Reader in, boolean useSmart) {
    super(in);
    offsetAtt = addAttribute(OffsetAttribute.class);
    termAtt = addAttribute(CharTermAttribute.class);
    typeAtt = addAttribute(TypeAttribute.class);
    _IKImplement = new IKSegmenter(input, useSmart);
  }

  /*
   * (non-Javadoc)
   * @see org.apache.lucene.analysis.TokenStream#incrementToken()
   */
  @Override
  public boolean incrementToken() throws IOException {
    // 清除所有的词元属性
    clearAttributes();
    Lexeme nextLexeme = _IKImplement.next();
    if (nextLexeme != null) {
      // 将Lexeme转成Attributes
      // 设置词元文本
      termAtt.append(nextLexeme.getLexemeText());
      // 设置词元长度
      termAtt.setLength(nextLexeme.getLength());
      // 设置词元位移
      offsetAtt.setOffset(nextLexeme.getBeginPosition(), nextLexeme.getEndPosition());
      // 记录分词的最后位置
      endPosition = nextLexeme.getEndPosition();
      // 记录词元分类
      typeAtt.setType(nextLexeme.getLexemeTypeString());
      // 返会true告知还有下个词元
      return true;
    }
    // 返会false告知词元输出完毕
    return false;
  }

  /*
   * (non-Javadoc)
   * @see org.apache.lucene.analysis.Tokenizer#reset(java.io.Reader)
   */
  @Override
  public void reset() throws IOException {
    super.reset();
    _IKImplement.reset(input);
  }

  @Override
  public final void end() {
    // set final offset
    int finalOffset = correctOffset(this.endPosition);
    offsetAtt.setOffset(finalOffset, finalOffset);
  }
}
